CHICAGO (CBS) — The family of Olga Maria Calderon, a Walgreens clerk stabbed to death in Wicker Park last week, wants to know why the store had removed security despite previous robberies, and why Cook County prosecutors allowed the teen now charged with her murder to be removed from electronic monitoring on a previous burglary case.

“This event has shattered our families, has left my children without a mother, and left me without the most important person in my life,” said Calderon’s husband, Israel Alvarado III. “This could have been prevented if people cared, if people weren’t so involved in their own agendas. There are so many dominoes that fell that led to this event that should not have even been in place.”

Frank Sommario, a partner at Romanucci & Blandin, the law firm representing Alvarado, said they are investigating the case and weighing a potential lawsuit over Calderon’s death.

Sommario said the law firm has learned the same Walgreens where Calderon worked was robbed in February, and hired a security guard, but that security was removed in March. He also said the young man now charged with killing Calderon on Sept. 6 robbed the same Walgreens just days earlier, but the store did not rehire a security guard, or notify employees who weren’t working at the time of the earlier holdup.

“Why did Walgreens not rehire security after this event? Why were other employees not notified? Why was there no security training or actions taken to equip the employees to deal with incidents such as this? And who made these disastrous decisions at Walgreens?” he said.

In a statement Wednesday afternoon, a Walgreens spokeswoman said the company continually evaluates security measures at all of its locations, and “additional security measures” were put in place at the Wicker Park store when it reopened after Calderon’s murder. However, the company has not answered questions about why there was no security guard at the store the day Calderon was killed.

“We continue to be very saddened by this tragic incident and again extend our deepest condolences to the family and loved ones of our team member. We have been in contact with the family and their representatives, offering our assistance and support. The safety of our customers and team members is our top priority, and Ms. Calderon’s family remains in our thoughts and prayers during this difficult time,” spokeswoman Erin Loverher wrote in an email.

Walgreens also said it has made counseling and other resources available to employees at the Wicker Park store after Calderon’s murder.

RELATED: Employee Fatally Stabbed At Wicker Park Walgreens | Sincere Williams, 18, Charged With Stabbing Employee At Wicker Park Walgreens To Death

Calderon’s life was cut short at 9:30 a.m. on Sept. 6, after she reported for work. Prosecutors have said Calderon, 32, was stocking the shelves at the Walgreens in Wicker Park when 18-year-old Sincere Williams walked up to her, grabbed her in a possible robbery attempt, and brutally stabbed her to death.

CBS 2 has learned that Williams was recently taken off of electronic monitoring for a separate burglary charge earlier this year when he was 17 – technically a juvenile. In May, Williams was arrested shortly after breaking into a Melrose Park gun store and grabbing 14 handguns. Just two months shy of his 18th birthday at the time, he was charged as juvenile, but in August, the gun store owner was notified Williams had violated the conditions of his electronic monitoring, but the court ordered that his monitoring bracelet be removed. The Cook County State’s Attorney didn’t object.

The Cook County State’s Attorney’s office said it had no objection to his release from house arrest based on “specific information presented to the court.”

Sommario said Calderon’s family want to know why prosecutors did not insist on keeping Williams on electronic monitoring.

“Why would the state’s attorney allow a person who robbed a gun store be allowed to walk free to commit other crimes? If it’s because he is schizophreinic, as is reported in the news, then why wasn’t he required to be electronically monitored while getting the necessary medical and psychological treatment?” Sommario said.

“Two minor children no longer have a mother to kiss, hug, and love. This brutal murder could and should have been prevented,” he added.

Community crisis responder Andrew Holmes also criticized several other businesses in the neighborhood, claiming they didn’t want to turn over surveillance video as detectives were investigating Calderon’s murder.

“It’s frustrating for the detectives when they come to try to help, and then you don’t want to help, because you don’t want your business robbed, but you’ve got a security system there to protect you? Why not protect the community, and not the money?” he said.

Alvarado said he wants to make sure what happened to his wife doesn’t happen to anyone else.

“We need to make sure that the mistakes that happened before this event never happen; that this person, if he needs help, that he gets it; that the state’s attorney does her job this time, and cares; to get justice for my wife, for my kids, and our family,” he said.

Alvarado said there aren’t enough words in the dictionary do describe his late wife.

“She was bright, funny. She cared about everybody; selfless, loving, caring,” she said. “She was one of the most selfless people I ever met. Everything she did was for her family. Everthing she was doing was for her kids.”

Friends and family have set up a GoFundMe page to help pay for Calderon’s funeral, and to support her children — an 11-year-old daughter and a 3-year-old son. The GoFundMe page has raised nearly $74,000 as of Wednesday morning.

“My daughter’s taking it as hard as can be, as is expected, but she’s strong like her mother. She’s very strong-willed like her mother, so she’s taking it in stride, but her mother is her best friend. They did everything together,” Alvarado said.

Alvarado said their 3-year-old son also understands what’s going on.

“He asks some of the hardest questions I’ve ever had to answer, but when he sees me emotional, he just puts his hand on my shoulder and says ‘Calm down.’ He doesn’t really fully grasp the gravity of what happened,” he said.

Prosecutors have said Williams planned ahead before he went into the Walgreens and killed Calderon, apparently bringing change of clothes. Detectives said a combination of police and home surveillance cameras show him walking back to his home in a new outfit.

According to court filings, Williams threw his bloody clothes in the bushes of a nearby house after killing Calderon, but he could be seen wearing the same shoes and with a blood stain on his pants.

“You can clearly see the Defendant’s face and the blood stain on his pants,” court documents read.

Officers found the knife that was believed to have been used to kill Calderon, as well as a second knife.

Prosecutors said recovered gloves with cuts in them also helped identify Williams. Officers said when they arrested him he had a cut on his hand. His mother told police she took him to the hospital to get stitches after the murder. She claimed her son told her he cut his hand on a fence.

Officers also executed a search warrant of Williams’ residence where they say they found a pair of shoes matching those worn in the videos and a shoe box containing packaging for a knife of the same brand and model number as the knife found when officers canvassed the area of the Walgreens.

Police have said Williams is suspected of robbing Calderon’s store four days before her killing, and also robbing another nearby Walgreens at North and Western avenues.

Williams is being held without bond at Cook County Jail.