GARY, Ind. (CBS) — Authorities in northwest Indiana were offering a $10,000 reward for information leading to the prosecution of a suspect or suspects in the murder of Gary Police Officer Jeffrey Westerfield, even though police have said publicly they’re “fairly confident” the suspect was arrested the same day Westerfield was slain.

WBBM Newsradio’s Mike Krauser reports a law enforcement source close to the investigation of Westerfield’s murder said authorities are confident they arrested the right person, but he also suggested there might be some sort of complications.

The suspect, arrested on Sunday, and officially called a “person of interest” in the case, has been held on an unrelated warrant at the Lake County Jail, so a 48-hour deadline to charge or release him does not apply.

Lake County Sheriff John Buncich, whose office is heading up the investigation, announced the $10,000 reward in the case on Wednesday. It was news to Gary Police Chief Wade Ingram, who said he would not speculate.

On Wednesday, more than 100 people – including police officers and volunteers – combed for evidence in the area where Westerfield was shot and killed inside his marked squad. The 19-year veteran of the Gary Police Department was shot and killed in the driver seat of his patrol car at 26th Avenue and Van Buren Place while responding to a call of shots fired at that location on Sunday.

The father of four was slain on his 47th birthday.

At the entrance to the Gary Police Department, a squad car has been parked at an angle, covered with flowers and draped in a black cloth as a memorial to Westerfield.