A 50-year-old man is dead following a two-vehicle collision in Ajax early Monday morning.

Police say a white BMW SUV T-boned a private security vehicle as it was exiting Highway 401 at Salem Road at around 3:15 a.m.

"It appears the security vehicle was exiting the highway coming eastbound when it was struck here in the middle of the intersection by the BMW," Const. George Tudos told reporters at the scene on Monday.

The impact of the collision resulted in the security vehicle hitting a concrete bridge wall. The driver, identified by police as Oshawa-resident Richard Lindsay, was pronounced dead at the scene.

The BMW continued on a short distance before knocking over a traffic signal pole. The driver suffered minor injuries and was later taken into custody.

Ajax-resident Melanie St. Louis, 42, has been charged with impaired operation causing death and exceeding the legal blood-alcohol limit.

St. Louis has been held for a bail hearing.

In a news release issued Monday afternoon, Durham Regional Police said that several hours prior to the fatal collision, Lindsay assisted officers in identifying a suspected drunk driver in a separate incident.

Lindsay’s assistance led to impaired charges against the driver, police said.

Salem Road from Achilles Road to north of Highway 401, as well as the Highway 401 eastbound exit and entrance ramps were closed to drivers while police collected evidence. The roads have since reopened.