Runaway electron generation, avoidance and suppression using Shattered Pellet Injection (SPI) have been studied for the first time at JET. Runaway generation is found to be possible in similar conditions as with Massive Gas Injection: high-Z species, low-elongation limiter configurations and high toroidal field favor runaway production. Runaway generation can be avoided if low-Z shattered pellets are fired early enough before the thermal quench. In-flight runaway beam suppression by SPI depends on the characteristics of the companion plasma sustained by the runaway beam itself and the shattered pellet composition. High-Z pellets tend to increase the runaway current decay rate and destabilize the beam vertically. Deuterium pellets decrease the apparent resistivity of the beam+companion plasma system, leading to a runaway current increase as in [1]. The final runaway collapse is mostly benign in D2-SPI cases, in contrast to high-Z-SPI cases. This difference despite higher runaway currents in D2-SPI cases will be discussed in the light of the amount of beam magnetic energy converted to kinetic energy at termination. [1] C. Paz-Soldan et al., Nucl Fusion 2019, 054001