A relative of a Japanese tourist stabbed to death in last year's car and knife rampage in Guam took the stand Wednesday, delivering an emotional account of the attack.

Shizuko Takeuchi, who was in Guam with more than 20 other Japanese in February 2013 to attend a nephew's wedding, recounted between sobs how her visit turned tragic when she was caught up in the rampage.

Takeuchi said she was in a convenience store in the main tourist district of Tumon when a speeding car allegedly driven by defendant Chad Ryan de Soto crashed outside after running over some Japanese tourists, killing one and injuring six.

De Soto is accused of then going on a stabbing spree, killing two Japanese tourists, including Takeuchi's niece Rie Sugiyama, and injuring five other people, including a resident.

"I was in panic," Takeuchi said, recalling how her sister approached her yelling that Sugiyama had been stabbed.

She said a store employee escorted them out the back door to safety.

Takeuchi broke down in tears as she was shown photos of Sugiyama and other victims she saw that night at the scene of the rampage.

De Soto has pleaded not guilty by reason of mental illness.