King County prosecutors filed charges against Mark W. Mullan on Thursday, including two counts of vehicular homicide, two counts of vehicular assault, and one count of reckless driving on Thursday.
Mullan, 50, was allegedly under the influence of alcohol when his truck struck a group of pedestrian's in Seattle's Wedgwood neighborhood on Monday.
Judy and Dennis Schulte, who recently moved to Washington from Indiana to be with their first grandchild, were killed in the collison.
Their daughter-in-law, Karina Ulriksen-Schulte and 10-day-old grandson Elias are still in critical condition at Harborview Medical Center.
"In the blink of an eye, a family was destroyed by the decision we allege that this defendant made to drink and drive," King County Prosecutor Dan Satterberg said in statement.
According to King County Prosecutors, Mullan's blood alcohol level was .22 percent, almost three times the legal limit.
Mullan pleaded guilty to driving under the influence in Seattle. He also has a pending DUI case in Snohomish County from October.
Mullan faces almost 20 years in prison if convicted under these charges filed Thursday. He is being held on bail of $2.5 million.