Left inset: Kevin Calamaco-Morales (Wyandotte County Detention Center). Right inset: Ana Juarez (GoFundMe). Background: The home in Kansas City, Kan., where Kevin Calamaco-Morales allegedly shot and killed his girlfriend Ana Juarez (Google Maps).

A Kansas man called his girlfriend 18 times in a span of two minutes and messaged her, calling her a "b—," before shooting the 20-year-old dead at a party he told her not to go to, cops say. The young woman was killed just days before her birthday.

"It must have been her crazy boyfriend," a witness said at the scene, according to Kevin Calamaco-Morales's arrest affidavit. Kansas City Police officers captured the statement on body camera.

Calamaco-Morales, 22, is charged with first-degree murder and criminal discharge of a firearm in connection with Ana Juarez's death. Witnesses said Juarez was at a Halloween party during the early morning hours of Nov. 1 when Calamaco-Morales began "blowing up" her phone with calls and texts, according to the affidavit.

A person who was at the party told police they noticed that Juarez "was not answering and declining whoever was calling or texting her" before hearing Calamaco-Morales began shouting her name from outside, the affidavit says. One of Juarez's friends told cops that they "thought the relationship was toxic" and that Calamaco-Morales was upset about Juarez going out to "house parties" for the holiday.

"[The friend] stated that Ana told her that Kevin is controlling and always wants to know where she is at and what she is doing and tells her what she can and can't do," the affidavit alleges. "Earlier in the week when [the friend] first asked Ana to come out for Halloween, Ana said Kevin wouldn't let her."

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Calamaco-Morales found out where Juarez was on the night of the shooting and began calling and texting her, according to police. He allegedly made 18 phone calls in a span of two minutes starting at 4:21 a.m., the affidavit says.

"You deada—?" Calamaco-Morales allegedly wrote in a Facebook message to Juarez.

"Deadaaa bro?" Calamaco-Morales repeated, according to the affidavit. "Ight bet," he allegedly said, adding, "You're out the f—ing house h— a— b—."

Police say Calamaco-Morales went up to the porch of the home where Juarez was partying and shot her dead as she exited through the front door. Juarez's friend who spoke to investigators said she "thinks that Kevin was the shooter because of his attitude towards and with Ana," noting how she "doesn't do what he wants" and has seen Kevin with guns before, according to the affidavit.

Multiple people identified Calamaco-Morales as the alleged suspect and police went to his house, where he was arrested. He was booked into jail by the Kansas City Police Department on a $500,000 bond and is scheduled to appear in court on Dec. 16.