A man beat and stabbed his Bronx girlfriend and her 14-year-old son to death, and then jumped in front of a train. That happened in the middle of February.

Last July a man in Queens fatally shot his wife, ex-wife, 6-year-old son and then himself.

The Commanding Officer of the NYPD's Domestic Violence Unit says police are trying to prevent horrific cases like these. However, Deputy Chief Kathleen White said it's not always easy,

"Almost 75 percent of our domestic violence homicides, they have no history with the police. We have no past history on the couples, the households," White said.

As of Sunday there had been 12 domestic violence murders in the city so far this year compared to eight in the same period last year. In all of 2018, 55 people were killed in domestic violence cases. Nineteen of those victims were shot to death and 22 stabbed to death. They others killed by blunt trauma or another deadly method according to police.

Deputy Chief Kathleen White said the NYPD now keeps a close watch on domestic violence offenders who have repeatedly abused partners or family members. Sometimes officers will even visit their homes.

"The DV recidivist list is something that is pretty new that we only started last year.  And that was if you commit a domestic violence crime three times or more you get on our recidivist list," White said.

A police analyst is also mapping out areas across the city that have high percentages of domestic violence with an eye toward having more D-V officers patrol those neighborhoods.

And it's not just adults. February is Teen Dating Violence Awareness and Prevention Month.

According to the U.S. Department of Health and Human Services about ten percent of teens who date have been physically abused by a boyfriend or girlfriend.

Chief White said those who are close to victims and aggressors must speak up.

"Be a friend talk to them. Get your other friends involved because sometimes they don't realize they are going down a path that isn't a good path to go down. And when their friends start to tell them that is not cool behavior, sometimes they see the light," White said.

Domestic violence officers across the city are responsible for helping adults and teens dealing with this issue that can turn deadly.

To find out more information you can go to safehorizon.org or call 1-800-621-HOPE (4673). You can also call 311.