A police chase that started in Butler County on Monday night ended with the suspect’s arrest at gunpoint just over the Allegheny County line.

But in his wake, the suspect, a California man, struck three vehicles, leaving one motorist badly injured.

Police in two counties still don’t know what caused 41-year-old Jose R. Rios of San Bernardino to flee officers in the first place.

The chase started shortly after 7 p.m. on Route 8 in Middlesex Township, police said. Officers were called there for a report of a suspicious vehicle.

Middlesex police spotted the vehicle going north on Route 8 and then turn onto Route 228 and head into Adams Township.

Officers tried to stop the car but he made a U-turn and got back onto Route 8, traveling south at speeds that topped 100 mph, police said.

Police in Adams Township and Mars joined Middlesex police in the high-speed pursuit.

During the chase, the suspect car hit two other vehicles just across the Butler-Allegheny County line in Richland Township.

The occupants in the other vehicles apparently were not hurt, authorities said.

The chase continued through Richland, said Northern Regional Police Chief Bob Amann. Minutes later, the suspect’s vehicle hit a car near the Northtowne Square shopping center.

Matthew Conte, 25, of Richland, the driver of that car, was flown to a Pittsburgh hospital with serious injuries, Amann said.

Officers, meanwhile, drew their weapons and arrested the suspect, who also was hurt in the wreck. The extent of his injuries was not known but not believed to be serious.

Amann said Middlesex Township police took custody of Rios. Middlesex police did not return telephone calls this morning.

Rios has been charged with aggravated assault, accidents involving injuries, reckless endangerment, escape and fleeing or attempting to elude police.

He remains in the Butler County Prison on $50,000 bail. Additionally, he is being held on a detainer from the Immigration and Customs Enforcement agency, which suspects he is an illegal immigrant.