Greyhound bus suspect is an illegal immigrant who has been deported before

Margarito Vargas-Rosas is in custody after allegedly threatening to kill fellow passengers on a Greyhound bus pursuit and leading police on a chase.

One passenger, Patrick Dodd, told the Chicago Tribune that the incident began when the man who said he had a gun started to threaten passengers riding in the back of the bus. Greyhound said in a statement that the incident began around 9:50 p.m. CT.

The suspect - described by Illinois State Police as "disorderly and possibly armed" - was arrested and detained after the bus came to a stop south of the Wisconsin state line near Wadsworth, in Lake County, Illinois, authorities said.

The Illinois State Police said they are investigating whether the man was carrying a gun.

Officials say they did not locate a weapon, however the Greyhound bus has been seized and will be thoroughly searched.

The bus eventually stopped on I-94 at Rt. 173.

Passengers called 911 while the altercation was taking place, but the bus driver didn't stop, unaware of the commotion on board and thinking that police were trying to stop someone else.

Racine County Sheriffs attempted to pull the bus over on I-94 near Hwy 20 but the bus continued southbound.

One passenger, Patrick Dodd, told the Chicago Tribune that the man pulled something out of his trousers that Dodd believed may have been a weapon.

"He was acting insane", passenger Patrick Dodd said, according to CNN affiliate WLS. "You're on a bus with a guy who said he had a gun", said Dodd.

Racine County Sheriff Christopher Schmaling says, the bus driver indicated he did not stop because, "he thought it was a training exercise by law enforcement, or thought he was going to stop someone". When he finally hit, that's when we were all hollering in the back "You need to stop".