This is what happens when you mix gender segregation, ignorance, and religious fundamentalism: death.
Saudis are so intent on keeping the genders separated, even at weddings, that they apparently have two separate halls, one for males and one for females. In a tragic case, the brother of the groom made the mistake of trying to make his way into the women's hall (along with some other relatives), so when the father of the bride witnessed this, he didn't just tell them to step away:
“He pulled his gun and shot at them.
“The groom’s brother was killed while the killer’s son was injured in exchange of fire between the two sides,” Sabq daily said without making clear if the incident affected the couple’s marriage.
Source: Emirates 24/7