The first day of legal marijuana use in Washington State was marred by an attempted robbery ending with two deaths at an alleged pot-growing facility just south of Seattle.

The possession of pot became legal in the state Thursday after voters passed a measure decriminalizing it in November. Day two kicked off with more celebrations under the Space Needle tower, the Seattle Post-Intelligencer reported, but the Pierce County Sheriff's Department investigated an attempted robbery in Puyallup at an alleged growing center foiled by a homeowner who shot two alleged burglars in front of his 9-year-old son.

Officers say they arrived at the home of the man, 35, Thursday to find two masked men dead on the floor and marijuana plants in the attic, ABC affiliate KOMO-TV News reported.

While the law passed in November made it legal to carry and consume marijuana, Sgt. Sean Whitcomb of the Seattle Police Department said cultivating and selling the drug outside of medical dispensaries is still a crime.

"When you're engaged in that type of criminal activity, there is an element of risk," Whitcomb told ABC News Friday.

The legislation leaves Washington in a "murky place," Whitcomb said. Smokers who have purchased marijuana from a street dealer are in the clear.

But the dealer "is still committing a felony," he said.

The U.S. Attorney's office in Seattle sent out a statement Wednesday reminding residents that pot is still illegal under federal law and cannot be brought onto federal property.

"Regardless of any changes in state law, including the change that will go into effect on December 6th in Washington State, growing, selling or possessing any amount of marijuana remains illegal under federal law," the memo from U.S. Attorney Jenny Durkan said.

Federal officials have not said whether they will take action in Colorado and Washington where possession laws now conflict with nationwide drug classifications, but Seattle Police told ABC News Thursday that federal agents were hands-off on pot smokers in the state.

In an ABC News poll released shortly after the election, 48 percent of Americans expressed support for legalizing marijuana.