The early morning commute was just getting under way on suburban Orange County's network of freeways when Melvin Lee Edwards pulled up to a stop sign near a busy off-ramp.

It was just after 5 a.m. and Edwards, 69, was on his way to work when, police say, a fleeing murder suspect forced him out of his BMW at gunpoint, marched him across the street and shot him three times from behind as horrified commuters watched.

The shooting was the second of three murders in a trail of carnage early Tuesday that spanned 25 miles -- but lasted just an hour. The shooter, 20-year-old Ali Syed, killed a woman in the home he shared with his parents, killed two drivers during carjackings, injured two others and shot up cars on a busy freeway interchange before committing suicide as police closed in, authorities said.

Syed, an unemployed part-time community college student, had no known motive and acted alone, said Tustin police Chief Scott Jordan. The first victim, a woman in her twenties, has not been identified and was not related to Syed, he said.

The violence began at 4:45 a.m., when deputies responded to a call from Ladera Ranch, a sleepy inland town about 55 miles southeast of Los Angeles. They found the woman shot multiple times.

Syed's parents were in the house at the time, fled the residence when shots were fired, and reported it, Jordan said.

From Ladera Ranch, the gunman headed north and pulled off Interstate 5 in Tustin, about 20 miles away, with a flat tire, police said.

A man who was waiting in a shopping center parking lot to carpool with his son saw Syed had a gun and tried to escape in his Cadillac, Jordan said. Syed ran after the car as it drove away and fired his shotgun through the back window, striking the driver in head but not killing him.

The driver "noticed that he was loading his shotgun, so he simply gets back in his car and tries to escape," Jordan said. "He's driving through the parking lot trying to get away and the suspect is actually chasing him on foot, taking shots at him."

Syed then crossed the street to a Mobil gas station, where he approached the driver of a pick-up who was filling his tank and asked for his keys, Jordan said.

"He says something to the effect of, `I've killed somebody. Today's my last day. I don't want to hurt you. Give me your keys,"' the police chief said. "He hands over the keys and he gets in the truck and leaves."

Syed got back on the freeway, where he pulled to the side of the road at the busy I-5 and State Route 55 interchange and began firing at commuters, Jordan said.

One driver was struck in the mouth and hand. He didn't have a cellphone, but was able to drive home and call police. Two other cars were hit but their drivers weren't injured, Jordan said.

"All of this is happening so quickly," he said, estimating that Syed shot at drivers from the side of the freeway transition for about a minute.

The shooter then exited the freeway in nearby Santa Ana but ran the curb and got his car stuck, authorities said.

He approached Edwards, of Laguna Hills, who was on his way to his Santa Ana business. Syed shot Edwards three times, including in the back of the head and the back, Jordan said.

Onlookers "tried to get away. They saw what was going on, they tried to get away and they called police," he said.

Syed took Edwards' BMW and next popped up at the Micro Center, a Tustin business, where he shot and killed construction worker Jeremy Lewis, 26, of Fullerton. Lewis' co-worker rushed to intervene and was shot in the arm, Jordan said.

Syed took the second construction worker's utility truck and fled to Orange, this time with California Highway Patrol officers in pursuit. He jumped from the moving utility truck at an intersection in Orange, about five miles away, and shot himself in the head, Jordan said.

"There really wasn't a confrontation at the very end," he said. "It happened so quickly."

A shotgun was recovered at the scene and is believed to be the only weapon used.

A message left at Syed's parents' home wasn't immediately returned on Tuesday.