CHICAGO (CBS) — Police Supt. Eddie Johnson on Thursday night addressed an incident in which he was found slumped over in his car in the early morning hours.

As CBS 2’s Jermont Terry reported, Johnson was back at work just hours after officers found him asleep behind the wheel of his sport-utility vehicle.

Johnson said the issue had to do with a mix-up in which he failed to take his blood pressure medication, and a feeling that he might faint that prompted him to pull over and rest.

Earlier, CPD spokesman Anthony Guglielmi said Johnson had pulled over and parked at 34th Place and Aberdeen Street near his home around 12:30 a.m., after “feeling lightheaded.”

A woman called 911 and reported seeing someone asleep in a Chevy Tahoe at a stop sign. Guglielmi said when officers arrived at the scene, they checked on Johnson in his vehicle.

“Officers did not observe any signs of impairment, and the Superintendent drove himself home,” Guglielmi stated in an email.

Walking swiftly to address the news media before a Police Board meeting Thursday night, Johnson was quick to try to put to rest his overnight encounter with the officers.

Johnson explained that while off duty on Wednesday night, he was out with a group of friends for dinner and was feeling fine when he left the restaurant. But close to home, he began feeling lightheaded – much as he when he nearly collapsed during a news conference in Englewood in 2017.

He admitted that he passed out in his vehicle with the engine running.

“Out of abundance of caution, I pulled over to the side and stopped, even though I was relatively close to home. Someone called 911 and reported a person asleep at the stop sign,” Johnson said. “Responding officers did come. They checked on me and confirmed that I could continue on my way. Also, that feeling that I was feeling had passed by that time.”

Johnson said he fell asleep when he pulled over.

“It’s just, your body kind of gives you a warning with the high blood pressure thing that you may pass out,” he said. “So I pulled over, stopped, and just rested myself until that feeling passed. I fell asleep – because remember, guys, we worked a long day that day.”

Johnson said he would have been better off having a driver with him last night, but both he and his usual driver had already worked all day. Because the driver has a young family that includes a student in the Chicago Public Schools where teachers are now on strike, Johnson let the driver go home.

Johnson added that he had visited his cardiologist twice earlier in the week to follow up on a blood clot that he experienced this summer.

“When I visited him on Tuesday, he adjusted my medication. It’s painful to admit this, but when he adjusted my medication, I took the old medication out for high blood pressure, but I failed to put the new medication in,” Johnson said. “So he wasn’t too happy with me today when he found out I hadn’t taken it, and I actually had forgotten to put it in there. So because of last night’s episode, I then visited my neurologist earlier today, and discovered I had elevated blood pressure – and that’s when I realized, I then switched the medications out.”

Johnson clarified that he had thrown away his old blood pressure medication when his cardiologist switched his prescription, but forgot to take the medication altogether on Wednesday rather than taking the new medication he had been prescribed. He said he needs to do better with his blood pressure medication.

After the incident early Thursday, Johnson visited his neurologist, who recommended that he go to the emergency room to get checked out.

“I assured him – we fought on the phone for a little while – that I would go, but I just felt it was incumbent on me to be here tonight for the Police Board meeting,” he said.

Meanwhile, Johnson said: “To avoid the appearance of impropriety and just have total transparency, I ordered the Bureau of Internal Affairs to conduct an internal investigation just to be transparent. As I’ve said before, every officer, regardless of rank, must uphold themselves to the highest of standards, and that includes me.”

A reporter asked Johnson why responding officers had not given him a Breathalyzer in the interest of transparency. Johnson said officers do not give Breathalyzer tests “just because” – only if there is probable cause such as someone looking impaired or smelling of alcohol or cannabis.

Responding officers also did not administer a field sobriety test – rather, they let their boss drive home.

Guglielmi said Johnson went to Rush University Medical Center after speaking Thursday night at Police Headquarters. He was released around 2 a.m. Friday, with doctors’ orders to “take it easy.”

Johnson has had a series of health issues since taking the top post at CPD. In June, he was treated for a small blood clot that was found in his lung during a routine test.

In August 2017, he received a kidney transplant from his son. He fainted at an awards ceremony a few days after returning to work that October, after suffering a blood pressure issue.

When he fell ill at the news conference 2017, spokesman said he had taken blood pressure medication on an empty stomach and felt sick, but the issue was not related to his kidney disease.

Johnson was diagnosed with kidney disease more than 30 years ago.