Three people died Saturday morning when two airplanes collided over Boulder County and crashed, according to the sheriff’s office.

Just before 9 a.m., emergency responders received calls about two planes colliding in midair east of Niwot, the sheriff’s office said in a news release. Two separate crash sites were found.

Claire Brown, 22, of Longmont, was working Saturday morning, feeding horses at a stable off of 95th Street and Niwot Road, when she heard a loud noise. Brown looked into the sky and saw to planes close together.

“At first, it looked like they were under control, then they spiraled down,” Brown said. “I saw some debris flying in the air too, I figured they had hit each other.”

Brown heard one plane crash. She called a friend who resides close to the crash site, and he told her that he also heard the crash. In just a moment, Brown said she heard sirens as responders raced to the scene.

“It is definitely unfortunate,” she said. “I knew those people were not alive after that. They weren’t terribly high, but as they were spiraling down the nose of the plane was heading straight down, pointing straight at the ground. You could tell that they had no control and that it was a bad crash. It happened so fast.”

One plane crashed near the 10,000 block of Niwot Road on the south side of the road, the sheriff’s office said. Two people onboard were dead. The other downed plane was found in the 9,700 block of Niwot Road on the north side. The pilot of the plane was dead.

The two planes involved were described by National Transportation Safety Board investigators as a Cessna 172 and a Sonex Xenos aircraft. The Sonex Xenos is a light, aluminum, low-wing homebuilt aircraft that seats two. The Cessna 172 Skyhawk is a popular single-engine aircraft that seats four.

None of the people involved was identified immediately.

Tom Falk and his wife, Susan, operate a 100-acre farm off of the 9500 block of Niwot Road. One plane crashed in an irrigation ditch about 300 yards from their home. The couple did not see or witness the crash, but they did hear and see the nearby emergency response.

“We just heard a lot of rescue coming,” he said.

Falk said that after the crash he walked their property, which is about five miles south, and a bit east, of the Vance Brand Airport, a Longmont-owned public-use airport.

“There’s always a lot of light aircraft coming around, but nothing unusual,” Falk said.

Falk said he couldn’t recall any prior plane crashes in the area.

“It’s unusual,” he said. “I feel bad that there are three families that are getting bad phone calls” with news of the crash.

The sheriff’s office, sheriff’s search and rescue, the coroner’s office, Mountain View Fire, Boulder Rural Fire Rescue, Boulder Emergency Squad, the State Patrol, the state Department of Transportation, Lifeline Helicopters, the Federal Aviation Administration and the National Transportation Safety Board responded.

An investigation is ongoing. Witnesses are asked to call 303-441-4763 or send an e-mail to lgalloway@bouldercounty.org.