PEOPLE confirms that Isaac Duran Infante admitted in court to strangling his ex-girlfriend with an electrical cord back on Dec. 22, 2016. The relationship between the pair made headlines in 2013.
A prosecution source tells PEOPLE Infante killed former DeWitt Clinton High School science teacher Felicia Barahona inside her apartment as their 4-year-old son, Miguel, watched.
After killing the 36-year-old mother and Afghanistan War veteran, Infante grabbed a different cord, and used it to kill Miguel.
Once the boy was dead, the source confirms that Infante left him face-down in a filled bathtub.
The source says Infante initially denied having any involvement in the deaths.
Prosecutors said he tried covering up his crimes by trying to make it look like Barahona killed Miguel before killing herself. Infante then grieved for his son while being questioned by detectives.
He told police he hadn’t been to Barahona’s apartment building since 2012, when their son was born.
Barahona’s relationship with Duran first became public in March 2013, after an internal investigative report was obtained by multiple local news outlets.
According to those reports, Barahona began having sex with Duran after he turned 18, though they later split in early 2012 before Miguel was born. Barahona was fired from Dewitt Clinton High School in August 2012.
Her family could not immediately be reached.
Infante will likely be sentenced to 25 years to life in prison when he returns to court on Dec. 19.
This article originally appeared on PEOPLE.