Questions persisted Thursday afternoon about a high-speed police chase that ended in a violent crash on Chicago's Far South Side.

The chain of events began in the south suburbs, and ended in the West Pullman neighborhood. A Pace bus was involved.

The crash happened at 7:19 p.m. in the 12700 block of South Halsted Street — at Vermont Street. Their conditions had all been stabilized as of Friday.

The City of Blue Island said it all started around 7 p.m. Wednesday, when a Blue Island police officer saw a sport-utility vehicle run a red light at the intersection of Ashland Avenue and Broadway Street. When the officer tried to stop the driver — a 31-year-old man — the driver took off.

The City of Blue Island said the chase lasted at least 90 seconds as the suspect drove off at a high rate of speed.

Chicago police said the driver went on to crash into the Pace Bus and two other cars at Halsted and Vermont streets. The driver had a 34-year-old man and a 26-year-old man in the car with him, police said.

The driver and the 34-year-old man were both taken to Advocate Christ Medical Center in Oak Lawn and was initially listed in critical condition. The 26-year-old man was taken to the same hospital in good condition, Chicago police said.

The City of Blue Island said 11 people were injured in the crash — also including six people on the bus and two in another car.

Pace said 20 people were on board the bus, and the bus driver was among those taken to the hospital. The bus itself sustained significant damage and was towed away.

A child was also among those injured in the crash.

The city of Blue Island say around 7 Wednesday night, a Blue Island Police officer saw a vehicle run a red light at the intersection of Broadway and Ashland.

The City of Blue Island said as a matter of standard procedure, the officer involved in the pursuit has been placed on paid administrative leave.

Arthur Lurigio, a professor of criminal justice and psychology at Loyola University Chicago, said in a split second, the officer needed to analyze whether this was worth to chase or not.

"Usually, a traffic violation doesn't necessarily warrant a chase," Lurigio said. "The basic criteria for the chase are one, is it safe to make the chase and two, was the crime serious enough to warrant a chase?"

Lurigio explained the reasons why running a red light might be cause for a pursuit.

"Maybe they quickly calculated the person might be intoxicated," he said. "They might be in a position of hurting someone with a weapon."

CBS News Chicago asked the City of Blue Island for its chase policy, and was told a Freedom of Information Act request would be required for it.