Neutering will very likely help... It well may have been play that got out of hand when one wanted to stop and the other didn't.... For now I'd go back to the seperate quarters for a bit and re-introduce them under supervision until you know they are ok with each other. Most times they work it out. Give them both space and affection and try again. Good luck. Male hormones are very likely a factor and getting those out is very likely to help...