(CNN)The parents of the youngest victim of the Boston Marathon bombings are making an emotional, passionate plea to take the death penalty off the table for the man convicted in the case. Last week, Dzhokhar Tsarnaev was found guilty on all 30 charges he faced related to the bombings at the 2013 race and the dramatic violence that dragged out for days afterward. A look at all of the charges . The sentencing phase begins Tuesday, a day after this year's edition of the landmark race. It is expected to last four weeks. The 13th Juror: Now it gets real . In a front-page opinion piece in The Boston Globe, Bill and Denise Richard wrote about the toll taken on their family after the death of their 8-year-old son, Martin. Their daughter, Jane, also was severely injured. "Our family has grieved, buried our young son, battled injuries, and endured numerous surgeries -- all while trying to rebuild lives that will never be the same," they said in the Globe column titled "To end the anguish, drop the death penalty." "We sat in the courtroom, day after day, bearing witness to overwhelming evidence that included graphic video and photographs, replicated bombs, and even the clothes our son wore his last day alive." They said they understood the "heinousness and brutality of the crimes committed." "We were there. We lived it. The defendant murdered our 8-year-old son, maimed our 7-year-old daughter, and stole part of our soul." But now the Richards are urging the Justice Department to bring the case to a close. "We are in favor of and would support the Department of Justice in taking the death penalty off the table in exchange for the defendant spending the rest of his life in prison without any possibility of release and waiving all of his rights to appeal," they wrote. They go on to say: "We know that the government has its reasons for seeking the death penalty, but the continued pursuit of that punishment could bring years of appeals and prolong reliving the most painful day of our lives. We hope our two remaining children do not have to grow up with the lingering, painful reminder of what the defendant took from them, which years of appeals would undoubtedly bring." Martin Richard and two others were killed and more 200 people wounded when a pair of bombs went off within 12 seconds of each other at the finish line on April 15, 2013. Tsarnaev was convicted last week, while his brother, Tamerlan, was killed in a shootout with police two years ago. The Richards never mention Tsarnaev by name. They stress that they were only speaking for themselves when they argue against the death penalty. "We believe that now is the time to turn the page, end the anguish, and look toward a better future -- for us, for Boston, and for the country," they wrote.
Parents of Martin Richard argue against death penalty for Dzhokhar Tsarnaev.
The 8-year-old boy was youngest of victims in the Boston Marathon bombings.
Sentencing phase for Tsarnaev begins next week.