JERSEY CITY, N.J. (CBSNewYork) — A man is being sought in the killings of his estranged girlfriend and their son in Jersey City, authorities said.

Jose Ronald Santos-Alvarez, 26, is wanted on two counts of first degree murder in the deaths of 27-year-old Monika M. Potoczniak and 4-year-old Christopher R. Potoczniak, the Hudson County Prosecutor’s Office said.

The two were found unconscious in their home on Lincoln Street around 5:30 p.m. Wednesday. They were both taken to the hospital where they were pronounced dead a short time later, authorities said.

The deaths were ruled a homicide after prosecutors said the medical examiner determined that Monika Potoczniak was strangled and her son was suffocated.

Neighbors said the family had lived in the apartment for about a year. They said the deaths are sad and shocking.

“Because it’s a very quiet neighborhood. Very nice, quiet neighborhood,” one man said.

An arrest warrant for Santos-Alvarez was issued Saturday. Prosecutors said he should not be approached and should be considered dangerous.

Anyone with information is asked to contact the Hudson County Prosecutor’s Office Homicide Unit at (201) 915-1345 or by email at hcpotips@hcpo.org. All contacts will be kept confidential.