From a press release:

King County Sheriff Deputies and bomb disposal units responded to a post blast involving significant injuries to a 26 year old male in unicorporated King County, just outside of Renton.

Upon arrival, the subject had been transported to Harborview with significant fragmentation injuries to his lower left leg and left forearm.

At approximately 4:23 a.m. Thursday, there was party in the Villa Townhomes in the Fairwood area of unincorporated Renton. The subject had a sparkler bomb (exact number of sparklers unknown at this time) wrapped in gray duct tape. The subject was in the middle of the street in the 14700 block of SE 176 ST and lit the sparkler bomb with a lighter.

The explosion was heard for several blocks to include Renton Fire Station 17 which is located on Petrovitsky.

The sparkler bomb appeared to have exploded quickly. Family and friends were present and provided immediate aid.

Renton Fire Station 17 responded prepared the male for transport and used a tourniquet for his leg.

At the scene, deputies collected duct tape and the wires and measured the farthest piece of fragmentation, which was approx. 125 feet from the blast.

The majority of tape and sparkler wires were located on the south side of the roadway with the some of the wire being imbedded in the trees near the apartment complex.  It is likely that the subject was facing south in the middle of the street.  The device was built with at least 50 sparklers.

Injuries sustained were open fractures to left leg and  area below the left knee and a deep penetrating injury to his left forearm. His left lower leg may be amputated below the knee.  When the subject arrived at Harborview, he was in critical condition.

This incident is still under investigation but it is a Class C Felony to convert common fireworks into something that creates an explosion.