Disturbed

The film follows Sarah Morrow, a mid-20's woman who has recently moved to Los Angeles, California. She is staying with a friend Leanne, who asks her to assist her and her friends in setting up and hosting a party/concert in an abandoned factory/warehouse. Sarah accepts the offer.
At the same time, police are on the hunt for a local serial killer known simply as Shoeless Red, who is wanted for the murders of three people, two of which were cops, and she is also suspected to be responsible for five others.
Sarah follows Leanne to the location of the party. There she meets Leanne's friends: Natasha, Emma, Jane, Fred, Paul, Colin & Harvey. Unbeknownst to the group, the location they have chosen is actually the home of Shoeless Red. 
Red returns home and sneaks in, avoiding the group of people.
Red kills Jane by impaling her on a wall.
Red kills Emma by bisecting the girl with two machetes while she is hanging by a chain around her neck.
Red decapitates Paul with a machete.
Red kills Natasha but crushing her head with a sledgehammer.
Red kills Fred by being hooked in the leg with a hook and chain, raised into the air upside down, and then disemboweled.
Red kills Leanne by beating her with a spiked club.
Red kills Harvey by impaling him with several steel rods.
Red kills Colin by beating him to death with her own hands and feet.
Sarah flees through the party/concert as all of the party-goers are oblivious to the approaching carnage. Red kills a few partiers before anyone realises what is going on. As everyone flees Red kills at least a dozen more people. Sarah manages escape, saving a young girl named Louise in the process. Outside she manages to contact the police from a payphone. The police arrive and Sarah, along with others are taken away. The cops enter the building slowly and one by one they find the corpses of the party-goers. Soon they find the corpses of Leanne & her friends. They however meet the same fate as they are picked off one-by-one by Red.
Red drives to the police station, armed with stolen firearms and some of her own blades.
Red storms the police station, killing anyone she sees.
Sarah flees the station with Louise and Red gives chase.