Police in Chesterfield are investigating after a woman was killed doing yard work while using a chainsaw Friday.According to the preliminary investigation, Marie Covey, 50, of Stratton, Vermont, was using a chainsaw when a portion of the tree separated and struck her, causing blunt-force trauma. The Chesterfield Police Department said she was not conscious or breathing when emergency personnel arrived. They attempted life-saving efforts, but Covey died on the scene. Police said the incident happened at about 10 a.m. Friday on Sheila Avenue in West Chesterfield.This is at least the fourth tree-related death in New Hampshire this year.Just last week, a member of a tree crew died while working at a Nashua home.The victim, 29-year-old Amilcar Lopez-Garcia, was a long-time employee at Leo’s Landscaping. Bedford police also said a tree trimmer was transported to a hospital with serious injuries, after they were electrocuted working with branches around power lines. Experts say tree work can be dangerous. "You always got to look out for broken branches because when you notch and back cut a tree, you always got to make sure that you have a safe zone, that everyone's clear. Definitely looking up to make sure everything's clear is very important because if you notch it back, cut a tree and there's a big hanger, it could come down and hit the cutter," said Joseph Parrot, owner of McClure's Tree Service LLC.Parrot warns if you ever have tree problems, leave it to a professional. "One thing that I always tell everyone, don't take a chance," Parrot said. "Call a professional tree guy."News 9 asked Chesterfield police if Covey was working as a member of a tree crew before the incident. They did not answer the question at this time.Police in Chesterfield and OSHA are still investigating exactly what happened.