The Gore Gore Girls

Nancy Weston (Amy Farrell), a reporter for The Globe, approaches Abraham Gentry (Frank Kress), an obnoxious private investigator, and offers him $25,000 on behalf of The Globe to investigate the brutal murder of stripper Suzie Cream Puff (Jackie Kroeger). She sweetens the deal with a $25,000 bonus for solving the case. Of course this comes contingent that The Globe gets the exclusive story. Gentry takes the case and begins the investigation of the murder with Weston in tow. When at the club, Gentry encounters a waitress, Marlene (Hedda Lubin), whose obnoxiousness rivals his. He gets through her to speak to another stripper and gets his first suspect, Joseph Carter.
Soon, another stripper, Candy Cane, gets murdered and Gentry expands his suspect list to Grout (Ray Sager), an unstable veteran who takes pride in crushing the heads of corpses he found when on the battlefields of Vietnam. He relieves tension by drawing faces on squashes and tomatoes and then crushing them with his bare hands. Gentry also suspects the leader of a radical feminist group that riots in the strip club, carrying banners with catchy phrases like "Lewd is Crude", "Quit with Tit" and "Women Right On!". Pickles, another stripper, is murdered and has her buttocks mutilated with a meat tenderizer hammer before having it salt and peppered. A badge with "Women Right On!" is found at the scene.
Meanwhile, Gentry buys Weston many drinks to keep her drunk and out of his way. During one of Weston's drunken episodes she admits she's attracted to Gentry. Gentry ignores this and concentrates on the case. His investigation takes him to the owner of the strip clubs in town, Mr. Marzdone Mobilie (Henny Youngman). Gentry then coerces Mobilie into holding an amateur stripper contest with a $1,000 prize, which also works as the beginning of a plan for Gentry's trap.
After having a few too many drinks, Gentry encourages Weston to perform the amateur stripper contest in which she goes all out by "taking it all off" and wins the $1,000 cash prize. Gentry accompany's Weston back to her apartment and lets her rest on her couch as he seemingly leaves. Soon, the killer arrives and Gentry, who anticipated that the killer would do just that, appears after hiding behind a door and takes off the killer's hood revealing Marlene. He also further reveals more when he pulls off her shirt revealing burn marks on her chest, literally obscuring her breasts. After a brief struggle, Marlene falls out a balcony window and lands on the street below where her head is crushed by an oncoming car.
Gentry then reveals his case in a long monologue to Nancy Weston about following the clues which Gout told him earlier about Marlene being burned in a fire which her breasts were burned off. This drew the conclusion that she was killing all those strippers out of jealousy and hatred to their own beauty which Marlene's was now taken from her. Weston is somewhat angry that Gentry used her as bait to trap Marlene into revealing herself as the killer, but accepts for the risk was worth it. Gentry and Weston profess their love for each other as she tells him that the story will make a great contribution to the Globe and both of them get "down to business" (making out), before Gentry looks at the camera and tells the viewers that it's over and to leave them alone.
The closing title card then appears reading: "We announce with pride: this movie is over!"

Question: What is Marlene's head crushed by?
Answer: Oncoming car