Police began looking for relatives of a man who killed himself by jumping in front of a Stockholm commuter train on Thursday afternoon. The search led them to an apartment in the suburbs to the south of the city.

Plain clothes officers entered the first-floor apartment by breaking a window at around 10pm on Thursday evening, and found the slain woman and her one-year-old son.

Forensic investigators continued to search the crime scene for clues on Friday morning, while colleagues knock on doors in the area in an effort to gather additional information about what police are investigating as a double homicide.

According to the police, much suggests that the man’s suicide and the double murder are related.

“In that way, they seem to be connected, but we’re still investigating. But just now there is much to suggest that a tragic relationship serves as the backdrop,” said Stockholm police spokesperson Mats Nylén to the TT news agency.

Nylén couldn’t say what the exact nature of the relationship was between those involved, nor would he divulge any details about how the woman and the infant were killed.

A neighbour who heard police break into the apartment where the two victims were found told TT that the young couple and child who lived there were pleasant and tranquil neighbours.

“I’ve never heard anything from their apartment. They were friendly neighbours who you greet and make small talk with. Ideal neighbours, I’d say,” she said.

“Now it feels really scary, partly because of being so close to something like this and partly because they were so easy-going and not the least bit out of the ordinary.”