Marcy,
The key to determining if Quantrill's riders killed your ancestor is to specify When and Where.

Please tell, as precisely as you can, the date or at least month and year Walland was killed.

Secondly, was Mr. Walland at home when he was killed? Lacking that information, where did the Walland's live? Name of town and/or county would be nice. It all hinges on how precise is your information about details regarding your ancestor's demise, especially in oral history passed down.