Abstract: At 8:00 a.m. on February 2, 2019, six employees (Employees #1 through #6) worked inside the Test Pad 7 Technical Control Room, located at the employer's Product Verification Center (PVC). A large lattice crawler whole crane testing occurred on Test Pad 7, and five of the employees, four of whom were based in Shady Grove and one of whom came from Wisconsin, had performed testing on a 300-ton Manitowoc MLC300 lattice crawler, referred to as Shop Order 6302, configured with a prototype 275.6-foot long lattice boom and a 275.6-foot long luffing jib. The area where the employees were working had high winds. While in Shop Order 6302's cab, Employee #1 noted sustained winds between 22 to 24 mph and a wind gust of 40 mph on Shop Order 6302's onboard display screen. Shop Order 6302 had an anemometer at the luffing jib's tip, which provided the wind speed information. Additionally, the Test Pad 7 Technical Control Room had a weather display console that received weather readings from a weather station mounted 40 to 50 feet above the ground on the main PVC building. Employee #2 saw a 40 mph wind reading on the weather display console inside the Test Pad 7 Technical Control Room just before 8 AM. Employees #2, #3, and #4 discussed the wind speeds with Employee #1, who said he would jackknife Shop Order 6302's boom and luffing jib after Employee #7 finished the carbody final inspection. Employee #2 then exited the Test Pad 7 Technical Control Room in order to move an assist crane sitting at the front side of and slightly north of the Test Pad 7 Technical Control Room. After walking about half way between the Test Pad 7 Technical Control Room and the assist crane, Employee #2 heard a loud bang from the boom of Shop Order 6302. Then, Employee #2 saw Shop Order 6302's boom start to collapse and yelled to warn the other five employees still inside the Test Pad 7 Technical Control Room. The failure started in the first boom insert above the boom butt. (The first three inserts made up the prototype part of the boom). The first insert collapsed to the left of (east of) the crane, and the boom, still vertical, hit the ground, causing the second and most of the third inserts to break apart. The luffing jib, still attached to the remaining boom, tipped to the south and east, where the luffing jib tip hit the ground south of the Test Pad 7 Technical Control Room, after which the rest of the boom and luffing jib fell to the east over the Test Pad 7 Technical Control Room but not hitting the Test Pad 7 Technical Control Room. The boom landed pointing northeast at the north side of the Test Pad 7 Technical Control Room, and the luffing jib landed directly behind the Test Pad 7 Technical Control Room and laid north to south. Finally, the fixed mast fell alongside the crane, landing parallel to the boom but at least 100 feet northwest of the boom. Employee #2 ran to the west and avoided physical injury. Employee #1 exited the Test Pad 7 Technical Control Room at the north door, fell to the ground, and sustained minor injury from falling. Employees #3, #4, #5, and #6 exited the Test Pad 7 Technical Control Room and ran to the east. Employee #5 sustained a minor injury to the shoulder. Employee #3 got struck by part of the luffing jib just behind a Scale Shack next to and south of the Test Pad 7 Technical Control Room. Employee #3 suffered immediately fatal multiple traumatic injuries. Employees #4 and #6 got struck by metal luffing jib straps and links east of (behind) the Test Pad 7 Technical Control Room. Employee #4 suffered multiple traumatic fatal injuries on site. Employee #6 got air lifted to York WellSpan Hospital where he succumbed to multiple traumatic injuries one week later.