Former UCLA doctoral student Mainak Sarkar shot and killed two people before taking his life Wednesday.

Before shooting UCLA professor William Klug, law enforcement officials believe Sarkar killed a woman in Minnesota. She is believed to be one of three people on a 'hit list' they found at Sarkar's home.

Klug was also on the list, along with another professor at the university who hasn't yet been identified, but is safe, police said. 

Hit lists are a common component in emotionally charged killings, but what do they mean, and who's supposed to read them?

For answers, Take Two spoke to Brian Van Brunt. He's a psychologist and trains mental health professionals to spot threats.

Press the blue play button above to hear the interview.