An Indiana high school footballer player, 16, has confessed to killing a pregnant cheerleader for failing to tell him she was six months along.

Aaron Trejo, 16, told police he was angry that she hid the pregnancy for six months so that she couldn’t have an abortion.

“I took action … I took her life,” Aaron said, according to Detective Gery Mullins in charging documents.

“Aaron explained that he stabbed Breana in the heart with a knife he brought from home. Aaron chose to use a knife because he thought it would kill Breana quickly,” Detective Mullins said in the documents. “Aaron stated that he put the black plastic bag over Breana, which he had brought from home for that purpose.

“Aaron Trejo said that he had been planning and thinking about killing Breana and the baby for about a week and had not told anybody. Aaron Trejo said that after he put Breana’s body in the dumpster, he walked to the river and threw Breana’s phone and his knife as far out into the river as he could,” the documents state.

Her mother last saw her on Saturday when she said she was going to meet the father of her unborn baby at 11pm but she never returned.

At 1am her mother realised her daughter wasn’t home and went to Aaron’s house but he said that Breana never turned up. She called police at 4:30am on Sunday.

Students at Mishawaka High School staged a walkout on Monday at 11am, the time when Breana’s body was found by police.

A GoFundMe campaign for funeral expenses has so far raised over $US4000.