Prosecutors allege untrained use of stump grinder was key factor Uploaded: Thu, Mar 4, 2021, 4:01 pm Time to read: about 1 minutes The owner of a Concord-based landscaping company was charged this week with two felonies in connection with the death of an employee at a worksite in San Ramon nearly three years ago, prosecutors said Thursday. (Stock image) The Contra Costa County District Attorney's Office and state investigators allege Segundo Collazos, owner of Amazon’s Landscaping Company, was negligent under the California Labor Code as an employer ahead of the death of Manuel Peralta on the job. Peralta, 68, of Antioch died while operating a rented tree stump grinder in San Ramon on April 9, 2018.