MURRIETA —— A Murrieta man died Tuesday when his pickup veered into oncoming traffic, slamming into a sport utility vehicle on Murrieta Hot Springs Road, injuring a woman and her three children, police said.

What caused the 9:20 a.m. crash is still being investigated.

"There's just no explanation right now as to why he crossed the center median," Murrieta police Officer Jay Froboese said. "There were no skid marks or any sign of braking before the impact."

Witnesses told police that the 1992 Chevrolet fullsize pickup was eastbound on Murrieta Hot Springs Road at an estimated 50 mph when it "very suddenly veered into traffic at about a 45-degree angle," Froboese said.

The pickup collided head-on with a westbound Toyota Sequoia SUV between Winchester Road and Calle Del Lago.

Combining the forward speeds of both vehicles when they collided, Froboese estimates the impact speed at between 80 and 100 mph.

The fronts of both vehicles were crushed, with the most severe impact occurring to the pickup. The engine was pushed into the passenger compartment.

Trent Allen Birchard, 24, died behind the wheel of the pickup, authorities said. He was not wearing a seat belt and the 1992 truck is not equipped with an air bag, Froboese said.

The driver of the SUV, Jennifer Lynn Sims, 25, of Winchester, was pinned in her vehicle and it took rescue personnel 50 minutes to get her out, Froboese said. Firefighters had to cut the top and doors off the Toyota so they could get to Sims and three children inside.

"The crash happened so quickly that (Sims) never even had a chance to stop or try to get out of the way," Froboese said. He added that there were no signs of tire skids or any evasive maneuvers made by either vehicles before impact.

Sims was wearing a seat belt and the front and side curtain air bags deployed inside the SUV, police said.

Officers closed a section of Murrieta Hot Springs Road so a medical helicopter could land and take Sims to Riverside County Regional Medical Center in Moreno Valley. Both of her legs were broken and she may have a broken pelvis, Froboese said.

"She was conscious when (officers and firefighters) got there, but unconscious by the time they could get her out and onto the helicopter," he said.

She regained consciousness after reaching the hospital, Froboese said Tuesday evening.

The woman's 2-year-old son, Joey, was hospitalized locally before being taken by helicopter to a hospital in Orange County for further treatment, Froboese said.

Sims' 1-year-old daughter, Brooklyn, and oldest son, Shane Sukol, 6, were also hospitalized.

The two youngest children were in car seats at the time of the crash and Shane was wearing a seat belt, police said.

Not long after the crash, Birchard's parents and a number of his friends arrived at the scene, police said. Officers learned that Birchard worked in construction doing tile work and was on his way to a friend's house for a tile job, Froboese said.

The crash and its subsequent investigation led to the closure of Murrieta Hot Springs Road in both directions until about 2 p.m.

Police ask that anyone who may have witnessed the crash contact Officer Frank LaVigne at (951) 461-6301.

This is the fifth fatal crash in Murrieta this year, Froboese said. Before this year, the city averaged one fatality every 12 to 15 months over the last six years, he said.

"The increase really isn't unexpected with the tremendous growth of population and traffic we've seen," he said.

Contact staff writer John Hall at (951) 676-4315, Ext. 2628, or jhall@californian.com.