Police say Albert Gutierrez, 23, of Petaluma arrived uninvited at a party in the 1000 block of Crinella Drive early this morning with an unidentified friend.
The two got into a fight with some of the partygoers and police say Gutierrez, who had a knife, tried to stab one of them. He then left, allegedly saying he would return with a gun.
Gutierrez went to a friend's house and returned to the party with Kellen Hoberg, a 25-year-old Petaluma resident, police said.
Police say Hoburg was carrying a gun and fired shots into the air at the party, then allegedly threatened several partygoers, striking one in the head with the gun.
Gutierrez allegedly tried another time to stab someone at the party.
The two party crashers fled when police arrived around 2:30 a.m. but were apprehended nearby, police said.
Hoburg was arrested for assault with a deadly weapon, brandishing a firearm and negligent discharge into the air. Gutierrez was arrested for assault with a deadly weapon.
Both were booked into Sonoma County Jail.