Detectives have traced the online threat that prompted the school's closure on Thursday, but they still don't know who is responsible.
The district said the post deeply rattled everyone in the community, and investigators spent much of Thursday looking for where it came from.
The threat first lit up the internet Wednesday at about 9 p.m.
"We received calls and emails as far away as Pennsylvania alerting us to this threat when they saw it on the social media website," said King County Sheriff Steve Strachan.
The online poster threatened to open fire on people in the school's common area, writing, "I will kill people until I'm stopped or run out of ammo."
"It's always scary when you hear things like that, because these are supposed to be safe places," said Skyline teacher Chuck Blagg.
With help from the FBI, detectives were able to trace the post to a proxy server in Sweden, which was used to hide the poster's origins.
"We have gotten some tips, we have gotten some leads and so far they have ruled out some possible suspects,but have not identified a specific person responsible," Strachan said.
Strachan said chances are the poster is a local and someone knows who he is. The threat is also worded just like one made against Meadowvale High School in Lynnwood in April.
Skyline will run on a modified schedule on Friday, with classes starting at 9:55 a.m. The campus will also be closed for lunch.
Anyone with information about the threats is asked to call police. Tipsters can remain anonymous.