Snyder went to the home and shot and killed the three others, authorities say.
"We can confirm that the suspect of these homicides is in his home on Brown Farm Way", Montgomery County police said in a tweet.
Over four hours after police initially responded to the incident, the area remained an "active scene", the county police department said on its official Twitter page.
According to a police press conference, Mr. Snyder had held his wife hostage over the weekend at their home at 22001 Brown Farm Way in Brookeville, Maryland.
Snyder reportedly fatally shot the neighbor, Mary Ann Olson, the neighbor's friend, Danny Lee Murphy, who was visiting from out of town, and a contractor, Craig Harold Shotwell, who was doing work on the neighbor's deck.
There were six people inside the house when Snyder began shooting, Manger said. "Our negotiators have been speaking with him via phone". His wife told investigators that Snyder had held her captive in their home for the weekend prior, and that she took an opportunity to flee the home on Monday.
Police are still searching the house for weapons and explosives based on the fact that Snider said during a conversation with negotiators. He asked the negotiator, 'Did they just break in to the front door?' and then hung up the phone. "At that point, officers outside the home heard a single gun shot". Manger also said police were not aware of any prior issues between Snyder and the victims.
According to police, there are multiple fatalities and the suspect is not in custody.