SEATTLE -- The Seattle Police Department is preparing for possible trouble this Friday.

Friday is May Day. You may remember protests on May Day 2013 that led to property damage and arrests. But Seattle Police Captain Chris Fowler called the last May Day "somewhat of a success."

"We're kind of going based on those ideas that what they did last year is kind of what will happen this year," said Captain Fowler.

With what's happening in Baltimore and a "Black Lives Matter" event planned on Friday, police expect to see a lot of people downtown. They've already met with at least one of the groups planning to march for workers' rights. They say that meeting went well.

Police said people have the right to express their protected free speech, but officers won't tolerate violence.

"It is the minute they start moving into violence of action or serious property damage, it doesn't matter what ideology they have, we have to take action just to protect the other protesters and protect the citizens and protect the officers," said Captain Fowler.

Some plain clothes officers might be in the crowd. If needed, police will work with State Patrol to stop people from marching on the Interstate like they did in a rally late last year.