You're correct. I had a momentary brain lapse. John and Mary Jane, not Allice, were children of Jackson and Mary Wallace who married Walker siblings: John married Allice Walker and Mary Jane married John Walker, his 2nd marriage.
John Wallace died by a self inflicted gun shot. Accident or suicide unknown. There were issues with eldest child that some have suggested led him to do the deed.
BTW John and Mary were married in Robertson Co. TX. Not sure if you were saying a city "Walker" or the county "Walker". You're date is good.