For two weekends in a row, parties in the college town of Davis have ended in violence.

On Saturday, one young man was stabbed and another struck in the head at a large party off campus, police said.

The previous weekend, uninvited guests at an on-campus fraternity party robbed students at gunpoint and stole a car, authorities said.

Davis police spokesman Lt. Paul Doroshov said the incidents may be partly due to social networking. Word of parties spreads fast, and outsiders cause trouble, he said.

“”With modern technology you can get hundreds of people to a spot within an hour,”” Doroshov said. Those who show up uninvited may be “”more likely to do something anti-social,”” he said.

At 12:48 a.m. Saturday, police received a call of a fight with chairs and bottles being thrown at the Avalon Apartments on Valdora Street, Doroshov said.

Most of the 200 partygoers, who had gathered around the swimming pool, scattered when police arrived, he said.

Officers found a 19-year-old man with a head injury near the pool. Another victim, 18, walked into the UC Davis Medical Center at 3:40 a.m. with a stab wound to the chest.

Both victims were from Stockton, police said.

Davis police Cpl. Mike Munoz said witness statements indicated two groups were shouting at each other across the pool and throwing bottles, with one group yelling “”Sac.””

Police said they didn’t know what the fight was about. They made no arrests. Doroshov said the party, like others thrown by young people, likely mushroomed beyond the hosts’ control.

In last weekend’s party violence, UC Davis police said there was an armed robbery at a fraternity house Feb. 20.

At about 2:15 a.m., police responded to the Nu Alpha Kappa fraternity house on Parkway Circle.

Two men had been asked to leave a party at the on-campus fraternity, police said. One of them approached four men outside, including two UC Davis students, and robbed them at gunpoint, they said.

The men reportedly took car keys from the fraternity house and stole a car. While attempting to flee, they crashed the car into the wall of a day care center, according to police.

Officers later found a gun in the day care playground.

“”The suspects had arrived at the NAK house as part of a group of men, all uninvited and unknown to the party hosts, and started causing trouble,”” police said in a university news release.

Officers apprehended Daniel Chavez, 19, of Soledad, at the scene. Chavez is not a student, they said.

Both Chavez and the other man are believed to be gang members, police said.

Chavez was arraigned on car theft and weapons charges Thursday, authorities said.

The other man escaped on foot. Police described him as a Latino male in his 20s, about 5-foot-8 with a medium build. He has a tattoo on his neck that says “”678,”” police said.

One of the robbery victims — a UC Davis sophomore who asked not to be identified for fear of retaliation — told The Bee he was shocked when he was robbed on campus.

But he said he understood why people would come to the relatively safe, affluent college town and cause trouble.

“”People come from distances to do crime here,”” he said, “”because they know we’re soft.””