I can't empty the Trash

I decided to delete my TimeMachine backups from an external hard drive to free up space on that drive. I put the backups in the Trash. I am now unable to empty the trash. I have tried to do so repeatedly without success. Trash says its deleting but will run for hours. The following popups are interspersed throughout the deletion process: "The operation can't be completed because the item 'share' is in use"; "The operation can't be completed because the item 'usr' in in use"; "The operation can't be completed because the item '2017-10-4-010820' in in use"; "The operation can't be completed because the item 'folders' is in use"; "The operation can't be completed because the item 'Library' is in use"; "The operation can't be completed because the item 'system' is in use."

- I have taken the following steps: I have run OnyX (I have the appropriate version for High Sierra) and Apple's Disk Utility. Both say the disk is OK. I have tried restarting. Nothing seems to help delete the Trash.