The US Festival finally found its audience today, as a sellout, mostly male crowd of 300,000 blanketed an outdoor concert bowl for an all-star bill of "heavy metal" rock music.

But law enforcement and medical officials said today's crowd was rowdy and injury-prone.

Authorities today said 81 persons were arrested at the festival, including about 50 felonies. The arrest total was revised downward from Saturday's report of 87.

The most serious crime was the fatal beating of a young man with an object that could have been a pipe or tire iron during a parking lot altercation early Sunday over an apparent drug deal. The victim, James Estell, 23, of Pomona, Calif., died at 3:25 p.m. (PDT) in San Bernardino General Hospital.

Deputies said David M. Planton, 22, of Stanton, Calif., and his 17-year-old girlfriend were arrested on suspicion of murder in the case.

Other arrests were for such offenses as drug possession and peddling, assaults, possession of weapons and car thefts.

Sheriff's Capt. Philip Schuyler attributed the arrests to individual wrongdoing, not crowd action.

Festival organizers said 1,287 persons were treated at first-aid centers today for injuries including wounds from random rock- and bottle throwing, drug and alcohol overdoses, severe sunburn and broken bones; 44 of the injuries were termed serious and eight people were hospitalized.

Another big crowd is expected Monday to see David Bowie, the Pretenders, Stevie Nicks and the Missing Persons. After a four-day intermission, the festival will conclude Saturday with a western music concert by Willie Nelson, Waylon Jennings and Emmylou Harris.

Today's show, featuring such performers as Van Halen, Judas Priest and Ozzy Osbourne, sold only about 100,000 advance tickets, but that was by far the best showing for the three-day rock festival.

Computer magnate Steve Wozniak, 31, who reportedly pumped $16 million into the extravaganza and hoped to attract 200,000 people daily, said today he was somewhat alarmed by the size of the crowd.

"I'm worried. I don't like it." He said he feared long lines at concessions and toilets, and added that despite the turnout, "we're going to lose money--somewhere between a lot and a little."

"Five million is a lot, $3 million is a little."

"I'm happy anyway," he added.