Matthew Thane, 18, was shot dead on Tuesday morning. Photo / GoFundMe

A 23-year-old male is believed to his taken his own life as a SWAT team descended on his house after he took a 5000km round trip to allegedly kill a teenager over an online gaming dispute.

Matthew Thane, 18, was shot dead about 6am on Tuesday at his home in Flower Mound, Texas.

On Wednesday night police in the California town of Pleasanton, close to 2700km away, moved to arrest the man they suspected was behind Thane's murder, but he is believed to have taken his own life before they could arrest him.

About 11pm he was found dead from a gunshot wound inside a house.

Evidence reportedly found on his mobile phone linked him to the murder in Texas, according to Bay Area publication the Mercury News.

Flower Mound detectives released a statement saying the suspected shooter of Thane wore a helmet and jeans, and was thought to have immediately fled the area.

A Bay Area police official told the Mercury News the suspected killer set a propane tank on fire outside Thane's house to lure him outside, where he was then shot dead.

Police believe the pair knew each other through online gaming and are investigating whether it was related to a dispute between the pair.

Where to get help:

• Lifeline: 0800 543 354 (available 24/7)
• Suicide Crisis Helpline: 0508 828 865 (0508 TAUTOKO) (available 24/7)
• Youth services: (06) 3555 906
• Youthline: 0800 376 633
• Kidsline: 0800 543 754 (available 24/7)
• Whatsup: 0800 942 8787 (1pm to 11pm)
• Depression helpline: 0800 111 757 (available 24/7)
• Rainbow Youth: (09) 376 4155
• Helpline: 1737

If it is an emergency and you feel like you or someone else is at risk, call 111.