A driver of a U-Haul truck carrying beer kegs through a tailgating area before the Yale-Harvard game Saturday suddenly accelerated, fatally striking a 30-year-old Massachusetts woman and injuring two other women, police said.

It's not clear why the driver sped up, New Haven Police spokesman David Hartman said. The truck then crashed into other U-Haul vans in the lot, an open playing field used for pre-game tailgating parties before Yale home games in New Haven.

Tim Walker of Pawtucket, R.I., said he was grilling sirloin tips when he heard the crash behind him. He turned and saw two people lying on the ground.

People huddled around them trying to help, according to a video that appears to have been recorded shortly after the accident and posted online. "We're not getting a pulse," said someone crouched near one victim, while the cameraman notes the ambulance hasn't arrived.

After emergency officials arrived, Walker said, he saw one victim being given CPR as she was taken away.

"The driver looked shocked. Absolutely shocked," Walker said. Police have not said whether alcohol was a factor.

"He didn't look intoxicated or anything like that," Walker added. "He had a dazed look like he had just hit someone."

Hartman said the driver was in police custody.

He said the woman who was killed was pronounced dead at about 10:15 a.m. at Yale-New Haven Hospital. Police did not immediately release her identity.

A second woman was listed in critical but stable condition at the hospital. The third woman suffered minor injuries.

The fans had gathered for the 128th game of the Ivy League rivalry, with Harvard looking for its fifth straight win over Yale. Three hours after the accident, the loud tailgating continued in the lot, with music blaring from large speakers and fans grilling hot dogs, sausage and hamburgers. Some students danced on top of other rental trucks.

The accident scene was cordoned off by yellow police tape, and a dozen numbered evidence placards were on the ground. The three rental trucks involved in the accident were still at the scene, stacked one against another from the collision.

At halftime of the game, with Harvard leading Yale, 24-7, the public address announcer at Yale Bowl informed the crowd of the accident and the woman's death, noting that it had been confirmed by the New Haven Police. He asked spectators to stand and observe a moment of silence.